ARLINGTON - A UT Arlington anthropologist is
gaining national recognition for a theory that climate change following massive
volcanic eruptions drove Neanderthals to extinction and cleared the way for
modern humans to thrive in Europe and Asia.

Assistant professor Naomi Cleghorn worked on a research team led by
Liubov Vitaliena Golovanova and Vladimir Borisovich Doronichev of the ANO
Laboratory of Prehistory in St. Petersburg, Russia. She is co-author on a paper
published in the October issue of Current Anthropology. Stories about
the research have recently appeared in The
New York Times and on the USA
Today and National
Geographic News websites.

"[W]e offer the hypothesis that the Neanderthal demise occurred abruptly (on a
geological time-scale) ... after the most powerful volcanic activity in western
Eurasia during the period of Neanderthal evolutionary history," the researchers
write. "[T]his catastrophe not only drastically destroyed the ecological niches
of Neanderthal populations but also caused their mass physical depopulation."

Evidence for the catastrophe comes from Mezmaiskaya cave in the Caucasus
Mountains of southern Russia, a site rich in Neanderthal bones and artifacts.
Recent excavations of the cave revealed two distinct layers of volcanic ash
that coincide with large-scale volcanic events that occurred around 40,000
years ago, the researchers say.

Geological layers containing the ashes also hold evidence of an abrupt and
potentially devastating climate change. Sediment samples from the two layers
reveal greatly reduced pollen concentrations compared to surrounding layers.
That's an indication of a dramatic shift to a cooler and dryer climate, the
researchers say. Further, the second of the two eruptions seems to mark the end
of Neanderthal presence at Mezmaiskaya. Numerous Neanderthal bones, stone tools
and the bones of prey animals have been found in the geological layers below
the second ash deposit, but none are found above it.

The theory that climate change led
to the Neanderthals extinction has been around for several years. The problem
with that theory, however, is that the Neanderthals had survived several
oscillations in environmental conditions in the past, Cleghorn said. Linking
their extinction with a massive volcanic eruption makes more sense than tying
it to a gradual climate change, the team believes.

"A volcanic event has a very rapid
impact on the landscape," Cleghorn said. "The environment literally crashed at
that point."

Cleghorn said her interest in the
work stems from a desire to understand how these close cousins of modern humans
could be wiped out.

The ash layers the team studied
correspond chronologically to what is known as the Campanian Ignimbrite
super-eruption which occurred around 40,000 years ago in modern day Italy, and
a smaller eruption thought to have occurred around the same time in the
Caucasus Mountains. The researchers argue that these eruptions caused a
"volcanic winter" as ash clouds obscured the sun's rays, possibly for
years. The climatic shift devastated the region's ecosystems, "possibly
resulting in the mass death of hominins and prey animals and the severe
alteration of foraging zones."

Anthropologists have long puzzled over the disappearance of the Neanderthals
and the apparently concurrent rise of modern humans. Was there some sort of
advantage that helped early modern humans out-compete their doomed cousins?
This research suggests that advantage may have been simple geographic location.

"Early moderns initially occupied the more southern parts of western Eurasia
and Africa and thus avoided much of the direct impact of the ... eruptions," the
researchers write.

While the researchers stress that more data from other areas in Eurasia are
needed to fully test the volcanic hypothesis, they believe the Mezmaiskaya cave
offers "important supporting evidence" for the idea of a volcanic extinction.